Fluid pressure operated apparatus



Sept. 9, 1969 J, F SAUNDERS EFAL 3,465,837

FLUID PRESSURE OPERTED APPARATUS 4 Sheets-Sheet l Filed Nov. 6, 1967 Sept. 9, 1969 J, F, SAUNDERS ET AL 3,465,837

FLUID PRESSURE OPERATED APPARATUS Filed Nov. 6, 196"?` 4 Sheets-Sheet 2 Sept. 9, 1969 J, F SAUNDERS EvTAL 3,465,837

FLUID PRESSURE OPERATED APPARATUS Filed Nov. 6, 196'? 4 Sheets-Sheet. 3

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FLUID PRESSURE OPERATED APPARATUS 4 Sheets-Sheet. 4

Filed Nov. 6, 1967 United States Patent O 3,465,837 FLUID PRESSURE OPERATED APPARATUS John Frank Saunders and Geoffrey Lionel Ryder, Filton, Bristol, England, assignors to Bristol Siddeley Engines Limited, Filton, Bristol, England, a British company Filed Nov. 6, 1967, Ser. No. 680,856 Claims priority, application Great Britain, Nov. 15, 1966, 51,212/ 66 Int. Cl. E21b 1/08, 3/12 U.S. Cl. 175-26 7 Claims ABSTRACT OF THE DISCLOSURE A downwardly-extensible ram piston between upper and lower chambers, each with fluid supplying ducting, a first valve which under rising pressure in the lower chamber closes ofi a lower chamber from a pressuresensitive element elsewhere in the fluid supply system, and a second valve which under falling pressure in the upper chamber opens the upper chamber to the supply ducting ofthe lower chamber.

This invention relates to uid pressure operated apparatus of the kind which include a ram piston under the control of opposing fluid pressures. Such apparatus may be used in borehole drilling apparatus to force the drill bit against the bottom of a borehole as a method of controlling the speed of a driving motor which is located near the bit, i.e., a down-hole motor.

A hydraulic turbodrill for sinking boreholes may comprise a drill bit driven by a hydraulic contra-rotating turbine, a speed-reducing gearbox mounted above the turbine, which transmits drive from the turbine to the drill bit, and a hydraulic ram device mounted above the gearbox, which varies the load on the drill bit in response to the rotational Speed of the drill bit. Intercommunicating oil systems supply oil to the gearbox for lubrication and oil to the ram device for operation of the ram piston.

During drilling, axial mechanical shocks are transmitted up the turbodrill casing to the ram device. In addition the ram piston may `suddenly accelerate downwards due to an abrupt advance by the drill bit, or the ram casing may suddenly accelerate upwards due to snatch of the drill pipe. Any of these happenings results in a transmission of oil from below the piston, causing a pressure rise in the oil system which can lead to overloading of gearbox oil seals and possibly other damage.

The present invention seeks to prevent such damage to the oil seals and elsewhere.

According to the invention, fluid pressure operated apparatus comprises:

(a) A ram piston arranged to slide in a casing under the control of liuid pressures in opposing operating chambers, a rst one of which receives the piston when the apparatus is extending and a second of which receives the piston when the apparatus contracts,

(b) First ducting for `supplying fluid under pressure to the first chamber via a first passage,

(c) Second ducting for supplying fluid under pressure to the second chamber,

(d) A pressure-sensitive element which is exposed to the pressure of fluid in the rst ducting and which it is desired to protect from a sudden increase in fluid pressure,

(e) A rst valve member movable in the first passage between a position in which the first passage is open, and a position in which the first passage is closed, and means normally urging this first valve member to open position, and

(f) A second valve member disposed in a second passage which permits communication between the first duct- 3,465,837 Patented Sept. 9, 1969 ing and the second chamber, the second valve member being movable between a position in which the second passage is closed and a position in which the second passage is open, and means normally urging this second valve member to closed position.

The two valve members may be two lands on a com mon spool.

Preferably the first and second passages are formed in the piston and extend in directions substantially parallel to the travel of the piston, and the first and second valve members are urged towards the first chamber to take up their respective open and closed positions. The means urging the valve members towards the first chamber may be a common spring plus the pressure difference between the two chambers, acting on the ends of the spool.

The two chambers may communicate through a relief valve, opening towards the second chamber, or the first ducting may communicate with the second ducting through a pressure relief valve which is located remotely from the piston.

Where the fluid in the first ducting is supplied from a reservoir having a flexible wall which is distended when the reservoir is full, the flexible wall constitutes the pressure-sensitive element to be protected from excessive distention.

Examples of apparatus according to the invention will now be described with reference to the accompanying diagrammatic drawings, in which:

FIGURES 1A, 1B and 1C are longitudinal sections in series through a hydraulic ram device, its control unit and a gearbox, all forming part of a hydraulic turbodrill; FIGURE 1A joins FIGURE 1B at the line A-B, and FIGURE 1B joins FIGURE lC at the line B-C;

FIGURE 2 is a longitudinal section through a frustoconical valve in the ram piston; and

FIGURE 3 is a part of FIGURE 1C with a cut-away showing an alternative position in the control unit for a relief valve.

FIGURE lA shows a hydraulic ram device comprising a piston 10 having upper and lower hollow piston rods 11, 12, which is arranged to slide in an upper casing 13 attached to the drill collars and drill pipe (not shown), under the control of opposing oil pressures on either face of the piston. The piston, which is provided with a sealing ring 14, is formed with two axial passages 15, 16, through which oil flow is controlled by, respectively, a spring-loaded oil pressure relief valve 17, and a valve 18 in the form of a spool provided with upper and lower lands 8, 9, which is urged downwards against a lower resilient seating 19 by a coiled spring 20. A radial passage 21 formed in the wall of the lower piston rod 12 connects the passage 16 with an annular axial oil duct 22 inside the piston rod 12, whilst a further passage 23 connects a space 24 above the piston with an axial oil duct 25 which extends centrally along the interior of the piston rod. The space 26 constitutes a lower cham-ber (the first chamber) into which the piston moves when the ram device extends, whilst the space 24, above the piston constitutes an upper chamber (the second chamber) into which the piston moves when the ram device contracts. The interiors of the piston rods provide a passage 27 for the drilling fluid (hereinafter referred to as mud) which drives the hydraulic turbine powering the Idrill bit of the turbodrill. The passage 21, and duct 22 constitute first ducting and the passage 23 and duct 25 constitute second ducting.

FIGURE 1B shows a lower casing 31 which is screwed to the lower piston rod 12. The annular duct 22 continues downwards as far as an upper support member 33 where it communicates with a number of oil transfer tubes 34. These tubes extend downwards through the member 33, an annular oil reservoir 35, and a lower support member 36, and then inwards across the mud passage 27 to the interior of a hollow centrebody 37.

The members 33, 36 which are annular, are joined together by an inner cylindrical sleeve member 38. To enable this assembly to be put into place, the lower casing 31 is in fact made in two or more pieces, screwed together. The oil reservoir 35 extends longitudinally between the members 33, 36, and radially between the casing 31 and a fiexible inner wall 39 which can assume a corrugated shape. When the reservoir is filled with oil, the wall 39 is distended inwards to lie in corrugations partially against the sleeve member 38 (as shown in broken lines at the left hand side of FIGURE 1B), and partially against a series of circumferentially spaced axial tubes 42. These tubes 42 lie between adjacent tubes 34. For example there may be four tubes 34 and eight tubes 42. The tubes 42 communicate at their ends with the mud passage 27 through channels 43, 44 and are provided with ports 45 through which mud can pass to act against the fiexible wall 39. A bleed passage 47 leads from the upper part of the reservoir to a spring-loaded pressure relief valve 48 which communicates with the channel 43. A restricted passage 49 connects the lower part of the reservoir with one of the transfer tubes 34.

FIGURE 1C shows the centrebody 37 surrounded by the mud passage 27 and extending downwards to a speed reduction gearbox which has an input shaft 56 connected to the high speed rotor (not shown) of a contrarotating hydraulic turbine below the gearbox and an output shaft 57 connected to a coupling member 58 arranged to drive the drill bit through the low speed rotor of the turbine. The gearbox is provided with a face seal 59 which seals the shaft 57 to the gearbox casing and with a face seal 60 which forms a seal between the shafts 56, 57.

The centrebody 37 houses an oil filter 61, an oil pump 62, and a control unit 63, which are connected in series by ducting 25a. The space 37a within the centrebody also acts as an oil sump; oil can enter or leave the gearbox via openings 64 and enter the filter 61 via a side inlet at 65. The pump 62, which receives oil from the filter and delivers it to the control unit, is driven by a shaft 66 directly from the input shaft of the gearbox. The control unit contains a flow control system whereby a variation in turbine speed, and therefore in the pump delivery, is used to vary the rate of flow of oil up or down the duct 25, oil in excess of requirement being bypassed for discharge into the centrebody sump via a dump pipe 67. The gearbox face seals 59, 60 are each exposed on one side to the oil pressure in the gearbox, and thus act as oil seals.

With the turbodrill in operation there are alternate phases of drilling and pay-off. During drilling, the string of drill pipe, to which the upper casing 13 (FIG- URE 1A is attached) is held stationary in the borehole, while the drill `bit is rotated by the turbine and urged downwards by the ram piston 10, The force with which the bit presses on the botom of the borehole is known as the bit weight. During drilling the rate of flow of pump delivery oil to the piston chamber 24 via the central duct 25 is controlled by the unit 63, and as the piston slowly descends to extend the ram device and maintain the required bit weight, oil from the piston chamber 26 is displaced via the passages 16, 21, annulus duct 22, and transfer tubes 34, to the centrebody sump 37a.

During pay-off of the drill string with the drill bit on the bottom of the borehole, the ram device is initially contracted by the excess weight of drill collars and the casing 13 moves downwards relative to the piston. As a result, oil is displaced from the chamber 24, passes downwards through the duct 25 to the control unit 63 where it is discharged through the pipe 67 into the sump 37, and then passes up the tubes 34 to reach the expanding lower chamber 26. The oil pressure in the sump 37a is maintained by the pressure of the mud acting against the reservoir.

Some of the mud being pumped down the passage 27 enters the ported tubes 42 via the channel 43 and urges the exible wall 39 radially outwards towards the casing 31, thus tending to squeeze the oil in the reservoir downwards through the passage 49 and then upwards through the relevant transfer tube 34, duct 22 and passages 21, 16, to the piston chamber 26 in order to replace oil which may be lost in operation.

During drilling, the drill bit may suddenly accelerate downwards, due for example to the `bit encountering an abrupt reduction in resistance to penetration of the formation being drilled. Without the valve 18, a sudden descent of the piston 10 could, despite the relief afforded by the valve 17, result in (a) a build-up of oil pressure in the lower chamber 26 causing a surge in oil pressure to travel down the duct 22 and into the sump 37a whence it enters the gearbox and overloads the shaft seals 59, 60 with consequent loss of oil and, at shallow drilling depths where the ambient pressure is relatively low, (b) cavitation in the upper chamber 24 resulting in hammering of the relief valve 17 against its seating, and consequent failure of that valve. A further danger is excessive distention of the flexible wall 39 of the oil reservoir against the ported tubes 42, resulting in premature wall failure.

The valve 18 operates in the following manner. During normal drilling, the piston is slowly descending with the valve spool abutting ites lower stop 19, as shown, so that oil displaced by the piston escapes past the lower land 9 and into the passage 21. In this condition the lower land 9 and the upper land 8, which each constitute a valve member, are respectively in their open and closed positions. The relief valve 17 does not normally permit a transfer of oil to the upper chamber, because of its designed spring loading. If the piston suddenly accelerates downwards, the sharp rise in oil pressure in the chamber 26 will urge the valve 18 upwards, and this response is quickened by the tendency of the valve 18 to lag behind the piston owing to inertia. This relative movement of the valve results in the lower land 9 taking up its closed position by forming a seal with the side of the passage 16 to cut off communication between the chamber 26 and the passage 21, and also in the upper land 8 taking up its open position by losing sealing contact with the side of the passage 16 so that communication past the upper land 8 is established between the passage 21 and the chamber 24. Consequently, in addition to some oil from the lower chamber 26 overcoming the relief valve 17 to reach the upper chamber 24, sufficient oil from the passage 21 can reach the upper chamber via the passage 16 to reduce the danger of cavitation in the chamber 24, this flow incidentally reducing the amount of oil in the reservoir. At the same time the quick isolation of the chamber 26 from the passage 21 by the lower land 9 ensures that no harmful surge of oil from the chamber 26 can travel down the duct 22 to reach the gearbox and cause a rise in pressure which would overload the shaft seals 59, 60. The initial surge of oil which does escape through the passage 21, before the lower land 9 seals off the chamber 26, will be too small and transient to reach the remote shaft seals 59, 60 in such a form as to cause them damage. The flexible wall 39 of the reservoir is nearer the source of surge of oil than the gearbox seals, but this disadvantage is offset by providing the flow-restricting passage 49 which acts to delay the ow of displaced oil into the reservoir.

The portion of the passage 16 which provides cornmunication between the chamber 26 and the passage 21, when the lower land 9 is in its open position as illustrated, constitutes the first passage, whilst that portion of the passage 16 which provides communication between the chamber 24 and the passage 21, when the upper land 8 is in its open position, constitutes the second passage.

If the casing 13 is jerked upwards during drilling, a similar effect occurs, but the protective action of the valve 18 is dependent only on the pressure difference in the chambers 24, 26 and is not helped by the valve inertia. However, the resulting slower response of the valve is not a serious disadvantage, because in practice upward acceleration of the casing is not as rapid as downward acceleration of the piston. The latter acceleration is assisted by the downwards force exerted on the upper end of the upper piston rod by the descending mud flow in the passage 27.

Referring to FIGURE 2, which shows a portion of a ram piston 70 provided with a frusto-conical valve 71, instead of the spool valve 18 illustrated in FIGURE lA, the valve 71 controls flow through a passage 72, the upper and lower ends of which communicate respectively with the upper and lower piston chambers 24, 26 of FIGURE 1A. A radial passage 73 connects the duct 22 `with an internal duct 74 of T-shape in the valve. A coiled spring 75 urges the valve 71 downwards against a frusto-conical seat 76. The valve is shown in its normal operating position, wherein it cuts oft communication between the piston chambers 24, 26, but permits flow through the T-duct 74 between the lower chamber 24 and the passage 73. Should the piston descend abruptly, the valve will lag behind, separating from its seat 76 so as to connect the passage 73 with the upper chamber 24 via the annulus portion of the passage 72 surrounding the valve. At the same time, the lower portion of the internal duct 74 becomes sealed off by the wall of the passage 72, and no longer communicates with the lower chamber 26.

The truste-conical valve 71 may be subjected to hammering against its seat, but provides a good seal, whereas the spool valve 18 is mechanically stronger and can have a resilient lower stop, but may provide a less effective seal due to manufacturing tolerances.

In the modification of FIGURE 3, the oil system, incorporating the piston chamber 26, duct 22 and tube 34, communicates with the pump delivery system, incorporating the duct 25 and piston chamber 24, via a spring-loaded pressure relief valve 75, which is located in the control unit 63 adjacent to the lower end of the tube 34. This valve replaces the relief valve 17 incorporated in the piston as shown in FIGURE 1A. Normally, the valve 75 is closed, and it opens only to permit priming of the pump delivery system. One ad- Vantage of this change in valve location is that the valve is remote from the piston chambers, and is less likely to be hammered against its seat by sudden changes in oil pressure arising from rapid irregular small movements of the piston caused by vibration during drilling. Also there is more space available for the valve spring, which can therefore be longer, and so provide a lower spring rate and thus a higher setting for the valve closed position. This reduces still further the danger of valve failure due to hammering.

A further advantage of this modification may be realised during pull-out from and insertion into the borehole, when it is advantageous to have the ram device in its contracted state in order to provide a stiffer assembly and to protect the otherwise exposed piston rod from damage. To obtain this advantage, the drill string is paid off to contract the ram device and then the casing 13 is given an initial upward jerk by the drill string causing upward displacement of the valve 18 relative to the piston, thus trapping the oil in the lower chamber 26 and thereby preventing subsequent expansion of the ram device. For subsequent expansion of the ram device, mud circulation is commenced with the drill bit on bottom and provided with a low bit weight. Thereupon the control unit 63 senses the overspeed of the bit and operates to raise the oil pressure in the chamber 24. This extends the ram device upwards, thereby expanding it.

We claim:

1. Fluid pressure operated apparatus comprising:

(a) a casing, and a piston within and projecting from the casing, the casing defining first and second opposing chambers separated by the piston, the piston advancing into the first chamber when the apparatus is extending and into the second chamber when the apparatus is contracting,

(b) first ducting adapted to supply fluid under pressure, a first passage connecting the first ducting to the first chamber, and a second passage connecting the first ducting to the second chamber,

(c) second ducting adapted to Supply fluid under pressure to the second chamber,

(d) a pressure-sensitive element which is exposed to the pressure of fluid in the first ducting and which it is desired to protect from a sudden increase in fluid pressure,

(e) a first valve member movable in the first passage by rising pressure in the first chamber from a position in which the first passage is open, to a position in which the first passage is closed, and means normally urging this first valve member to open position,

(f) and a second valve member movable in the second passage by falling pressure in the second chamber from a position in which the second passage is closed to a position in which the second passage is open, and means normally urging this second valve member to closed position.

2. Apparatus according to claim 1, in which the two Valve members are two lands on a common spool.

3. Apparatus according to claim 1, in which the first and second passages are formed in the piston and extend in directions substantially parallel to the travel of the piston, and in which the first and second valve members are urged towards the first chamber to take up their respective open and closed positions.

4. Apparatus according to claim 1, including a further passage connecting the first and second chambers and a relief valve in this further passage, arranged to open towards the second chamber.

5. Apparatus according to claim 1, including a reservoir communicating with the first ducting, and having a fiexible wall which constitutes the pressure-sensitive element.

6. Apparatus according to claim 1, in which the pressure-sensitive element comprises an oil seal.

7. A turbodrill including a drill bit driven by a hydraulic contra-rotating turbine, a speed-reducing gearbox mounted above the turbine, which transmits drive from the turbine to the drill bit, and a hydraulic ram device mounted above the gearbox, which varies the load on the drill bit in response to the rotational speed of the drill bit, the ram device being constituted by apparatus according to claim 1.

References Cited UNITED STATES PATENTS 3,138,214 6/1964 Bridwell 175--94 X 3,203,184 8/1965 Whittle 175--94 X 3,233,689 2/ 1966 Whittle 175-94 3,291,230 12/ 1966 Cullen 175-107 X NILE C. BYERS, I R., Primary Examiner 

